This invention relates to organometallic compounds. More specifically, this invention relates to organometallic compounds containing at least one fluorenyl ligand. In another aspect, this invention relates to polymerization catalyst systems which contain organometallic fluorenyl compounds. In still another aspect, this invention relates to a method for polymerizing olefins using such organometallic fluorenyl compounds and to the polymers resulting from such polymerizations.
Since the discovery of ferrocene in 1951, a number of metallocenes have been prepared by the combination of compounds having cyclopentadienyl structure with various transition metals. The term xe2x80x9ccyclopentadienyl structurexe2x80x9d as used herein refers to the following structure. 
The term xe2x80x9ccyclopentadiene-type compoundsxe2x80x9d as used herein refers to compounds containing the cyclopentadiene structure. Examples include unsubstituted cyclopentadiene, unsubstituted indene, unsubstituted fluorene, and substituted varieties of such compounds. Also included is tetrahydro indene.
Many of the cyclopentadiene-type metallocenes have been found useful in catalyst systems for the polymerization of olefins. It has been noted in the art that variations in the chemical structure of such cyclopentadienyl-type metallocenes can have significant effects upon the suitability of the metallocene as a polymerization catalyst. For example, the size and substitutions on cyclopentadienyl-type ligands has been found to affect the activity of the catalyst, the stereoselectivity of the catalyst, the stability of the catalyst, and other properties of the resulting polymer; however, the effects of various substituents is still largely an empirical matter, that is, experiments must be conducted in order to determine just what affect a particular variation will have upon a particular type of cyclopentadienyl-type metallocene. Some examples of some cyclopentadienyl-type metallocenes are disclosed in U.S. Pat. Nos. 4,530,914; 4,808,561; and 4,892,851, the disclosures of which are incorporated herein by reference.
While there are references in the prior art which have envisioned metallocenes containing fluorenyl groups, only a very limited number of fluorenyl-containing metallocenes have actually been prepared prior to the present invention. The Journal of Organometallic Chemistry, Vol. 113, pages 331-339 (1976), the disclosure of which is incorporated herein by reference, discloses preparing bis-fluorenyl zirconium dichloride and bis-fluorenyl zirconium dimethyl. U.S. Pat. No. 4,892,851 and the New Journal of Chemistry, Vol. 14, pages 499-503, dated 1990, the disclosures of which are incorporated herein by reference, each disclose preparing a metallocene from the ligand 1,1-dimethylmethylene-1-(fluorenyl)-1-(cyclopentadienyl). The New Journal of Chemistry article also discloses preparing a similar compound in which the cyclopentadienyl radical has a methyl substituent in the number 3 position. The term fluorenyl as used herein refers to 9-fluorenyl unless indicated otherwise.
An object of the present invention is to provide certain new fluorenyl-containing metallocenes. Another object of the present invention is to provide a method for preparing new fluorenyl-type metallocenes. Still another object of the present invention is to provide polymerization catalysts employing fluorenyl-type metallocenes. Still yet another object of the present invention is to provide processes for the polymerization of olefins using fluorenyl-type metallocene catalyst systems. Still yet another object of the present invention is to provide polymers produced using such fluorenyl-containing metallocene catalysts.
In accordance with the present invention, there are provided new metallocenes of the formula Rxe2x80x3x(FlRn)(CpRm)MQk wherein Fl is a fluorenyl radical, Cp is a cyclopentadienyl, indenyl, tetrahydro indenyl, or fluorenyl radical, each R is the same or different and is an organo radical having 1 to 20 carbon atoms, Rxe2x80x3 is a structural bridge linking (FlRn) and (CpRm), M is metal selected from the group consisting of IVB, VB, and VIB metals of the Periodic Table, each Q is the same or different and is selected from the group consisting of hydrocarbyl or hydrocarbyloxy radicals having 1 to 20 carbon atoms and halogens, x is 1 or 0, k is an integer sufficient to fill out the remaining valences of M, n is an integer in the range of 0 to 7, m is an integer in the range of 0 to 7, further characterized by the fact that if (CpRm) is unsubstituted fluorenyl and x is 0, then n is 1 to 7, and if (CpRm) is unsubstituted cyclopentadienyl or 3-methylcyclopentadienyl and Rxe2x80x3 is 1,1-dimethyl-methylene, then n=1 to 7.
In accordance with another aspect of the present invention, there is provided a method for forming fluorenyl-containing metallocenes comprising reacting an alkali metal salt of the selected fluorenyl compound with a transition metal compound of the formula Mqk in the presence of a non-halogenated solvent for the fluorenyl salt which solvent is non-coordinating with the transition metal halide.
In accordance with still another aspect of the present invention, there is provided a process for the polymerization of olefins comprising contacting said olefins under suitable reaction conditions with a catalyst system comprising a fluorenyl-containing metallocene as described above in combination with a suitable organoaluminum co-catalyst.
Still further in accordance with the present invention there is provided the polymer products resulting from such polymerizations.
The novel metallocenes provided in accordance with the present invention fall into two broad general categories. One category involves metallocenes in which a fluorenyl radical, either substituted or unsubstituted, is bonded to another cyclopentadienyl-type radical by a bridging structure Rxe2x80x3. These metallocenes are referred to herein as bridged metallocenes. The other category deals with metallocenes which are unbridged, that is the fluorenyl radical ligand and the other cyclopentadienyl-type ligands are bound to the metal but not to each other. These metallocenes are referred to as unbridged metallocenes. Methods for preparing fluorenyl-containing cyclopentadiene-type compounds which can be used in making the metallocenes are disclosed in the aforementioned U.S. patent application Ser. No. 697,363.
The metal, M is selected from the group 4 or 6 metals of the Periodic Table. The currently preferred metals include titanium, zirconium, hafnium, chromium, and vanadium. The Rxe2x80x3 can be selected from any suitable bridging structure. Typical examples include hydrocarbyl and heteroatom containing alkylene radicals, germanium, silicon, phosphorus, boron, aluminum, tin, oxygen, nitrogen, and the like. The Rxe2x80x3 bridge when hydrocarbyl can be aromatic in nature, such as a phenyl substituted alkylene; however, the currently preferred modes employ aliphatic alkylene bridges. The currently most preferred bridges are hydrocarbyl or heteroatom containing alkylene radical having 1 to 6 carbon atoms. In an especially preferred embodiment k is equal to the valence of M minus 2.
The substituents R can be selected from a wide range of substituents. In the preferred embodiments the substituents R are each independently selected from hydrocarbyl radicals having 1 to 20 carbon atoms. In a particularly preferred embodiment, the hydrocarbyl radicals R are alkyl radicals. More preferably the alkyl R radicals have 1 to 5 carbon atoms. Each Q is a hydrocarbyl radical such as, for example, aryl, alkyl, alkenyl, alkaryl, or arylalkyl radical having from 1 to 20 carbon atoms, hydrocarbyloxy radicals having 1 to 20 carbon atoms, or halogen.
Exemplary Q hydrocarbyl radicals include methyl, ethyl, propyl, butyl, amyl, isoamyl, hexyl, isobutyl, heptyl, octyl, nonyl, decyl, cetyl, 2-ethylhexyl, phenyl, and the like. Exemplary halogen atoms include chlorine, bromine, fluorine, and iodine and of these halogen atoms, chlorine is currently preferred. Exemplary hydrocarboxy radicals include methoxy, ethoxy, propoxy, butoxy, amyloxy, and the like.
Illustrative, but non-limiting examples of unbridged metallocenes falling within the scope of the above formula include bis(1-methyl fluorenyl) zirconium dichloride, bis(1-methyl fluorenyl) zirconium dimethyl, bis(1-methyl fluorenyl) hafnium dichloride, bis(1-t-butyl fluorenyl)zirconium dichloride, bis(2-ethyl fluorenyl) zirconium dichloride, bis(4-methyl fluorenyl)zirconium dichloride, bis(4-methyl fluorenyl)hafnium dichloride, bis(2-t-butyl fluorenyl) zirconium dichloride, bis(4-t-butyl fluorenyl)zirconium dichloride, bis(2,7-di-t-butyl fluorenyl)zirconium dichloride, bis(2,7-di-t-butyl-4-methyl fluorenyl)zirconium dichloride, and the like.
Illustrative, but non-limiting examples of metallocenes containing bridged fluorenyl ligands include for example (1,1-difluorenylmethane)zirconium dichloride, (1,2-difluorenyl)ethane zirconium dichloride, (1,3-difluorenylpropane)zirconium dichloride, (1,2-difluorenylethane)hafnium dichloride, (1,3-difluorenylpropane)hafnium dichloride, (1-fluorenyl-2-methyl-2-fluorenylethane)zirconium dichloride, dimethylsilyldifluorenyl zirconium dichloride, (1,2-di(1-methyl fluorenyl)ethane)zirconium dichloride, (1,2-di(1-methyl fluorenyl) ethane) hafnium dichloride, (1,2-di(2-ethyl fluorenyl)ethane)zirconium dichloride, (1,2-di(2-t-butyl fluorenyl)ethane)zirconium dichloride, (1,2-di(2-t-butyl fluorenyl)ethane)hafnium dichloride, (1,2-di(1-t-butyl fluorenyl)ethane) zirconium dichloride, (1,2-di(4-methyl fluorenyl) ethane) zirconium dichloride, (1,2-di(4-methyl fluorenyl)ethane) hafnium dichloride, (1,2-di(4-t-butyl fluorenyl)ethane) zirconium dichloride, 1-(fluorenyl)-1-(cyclopentadienyl)methane zirconium dichloride, 1-(fluorenyl)-1-(cyclopentadienyl)methane hafnium dichloride, 1-(2,7-di-t-butyl fluorenyl)-1-(cyclopentadienyl)methane zirconium dichloride, (1-fluorenyl-2-cyclopehtadienylethane)zirconium dichloride, (1-fluorenyl-2-(3-methyl cyclopentadiebyl)ethane)zirconium dichloride, (1-fluorenyl-2-indenyl ethane)zirconium dichloride, (1-fluorenyl-2-indenyl ethane)hafnium dichloride, (1-fluorenyl-2-methyl-2-indenyl ethane)zirconium dichloride, (1-fluorenyl-2-methyl-2-indenyl ethane)hafnium dichloride, (bis-fluorenylmethane)vanadium dichloride, (1,2-difluorenyl ethane)vanadium dichloride, (1-fluorenyl-1-cyclopentadienyl methane) zirconium trichloride, (1-fluorenyl-2-methyl-2-(3-methyl cyclopentadienyl)ethane)zirconium dichloride, (1-(1-methyl fluorenyl)-2-(4-methyl fluorenyl)ethane)zirconium dichloride, (1-(2,7-di-t-butyl fluorenyl)-2-(fluorenyl)ethane)zirconium dichloride, (1,2-di(2,7-di-t-butyl-4-methyl fluorenyl)ethane)zirconium dichloride, and the like.
Particularly preferred metallocene species include bridged and unbridged metallocenes containing at least one substituted fluorenyl radical, i.e., there is at least one FlR wherein n is 1 to 7.
The inventive metallocenes as well as related metallocenes can be prepared by reacting an alkali metal salt of the bridged or unbridged fluorenyl compounds with a suitable transition metal compound in a suitable solvent under suitable reaction conditions.
The term transition metal compound as used herein includes compounds of the formula MQk wherein M, Q, and k are as defined above. Some non-limiting examples include zirconium tetrachloride, hafnium tetrachloride, cyclopentadienyl zirconium trichloride, fluorenyl zirconium trichloride, 3-methylcyclopentadienyl zirconium trichloride, indenyl zirconium trichloride, 4-methyl fluorenyl zirconium trichloride, and the like.
The currently preferred unbridged metallocenes are prepared by reacting a substituted fluorenyl alkali metal salt with an inorganic halide of the Group IVB, V B, VIB metals to form a bis(substituted fluorenyl) metal halide. In an especially preferred embodiment bridged a fluorenyl compounds of the formula (FlRn)Rxe2x80x3(CpRm) are used wherein Fl, R, Rxe2x80x3, and m are as defined above, and where n is 1 to 7, most preferably 1 to 4.
Metallocenes in which Q is other than a halogen can be readily prepared by reacting the halide form of the metallocene with an alkali metal salt of the hydrocarbyl or hydrocarbyloxy radical under conditions as have been used in the past for forming such ligands in prior art E metallocenes. See, for example, the aforemention J. Organomet. Chem. 113, 331-339 (1976). Another approach involves reacting a compound of the formula MQk wherein at least one Q is hydrocarbyl or hydrocarbyloxy with the alkali metal salt of the bridged or unbridged fluorenyl compound.
One embodiment of the present invention involves carrying out the reaction of the fluorenyl-containing salt and the transition metal compound in the presence of a liquid diluent which is non-halogenated and non-coordinating toward the transition metal compound. Examples of such suitable liquid include hydrocarbons such as toluene, pentane, or hexane as well as non-cyclic ether compounds such as diethylether. It has been found that the use of such non-halogenated non-coordinating solvents generally allows one to obtain large amounts of substantially pure metallocenes and in a more stable form; and also often allows the to reaction to be conducted under higher temperature conditions, than when THF is used as the diluent. In an especially preferred embodiment the fluorenyl-containing salt used as a ligand is also prepared in a liquid diluent that is non-halogenated and non-coordinating toward the transition metal.
The formation of the alkali metal salt of the bridged or unbridged fluorenyl compound can be formed using generally any technique known in the art. For example, such can be prepared by reacting an alkali metal alkyl with the cyclopentadienyl type compounds, the bridged compounds having two cyclopentadienyl-type radicals per molecule. The molar ratio of the alkali metal alkyl to the cyclopentadienyl type radicals present can vary, generally however, the ratio would be in the range of about 0.5/1 to about 1.5/1, still more preferably about 1/1. Typically, the alkali metal of the alkali metal alkyl would be selected from sodium, potassium, and lithium, and the alkyl group would have 1 to 8 carbon atoms, more preferably 1 to 4 carbon atoms. Preferably if the fluorenyl salt is formed using tetrahydrofuran (THF) as the liquid solvent, the salt is isolated and substantially all of the THF is removed before the salt is contacted with the transition metal halide. The molar ratio of the bridged or unbridged fluorenyl compound to the transition metal compound can vary over a wide range depending upon the results desired. Typically, however, when an unbridged fluorenyl compound is used, the molar ratio of the unbridged fluorenyl compound to the transition metal compound is in the range of from about 1 to 1 to about 2 to 1 and when a bridged fluorenyl compound is used the molar ratio of the bridged fluorenyl compound to the transition metal compound is about 1 to 1.
The resulting metallocene can be recovered and purified using conventional techniques known in the art such as filtration, extraction, crystallization, and re-crystallization. It is generally desirable to recover the metallocene in a form that is free of any substantial amount of by-product impurities. Accordingly, recrystallization and fractional crystallization to obtain relatively pure metallocenes is desireable. Dichloromethane has been found to be particularly useful for such recrystallizations. As a general rule, it has been found that the metallocenes based on unbridged fluorenyl compounds are less stable than the metallocene compounds formed from bridged fluorenyl compounds. Since the stability of the various metallocenes varies, it is generally desirable to use the metallocenes soon after their preparation or at least to store the metallocene under conditions favoring their stability. For example the metallocenes can generally be stored at low temperature, i.e. below 0xc2x0 C. in the absence of oxygen or water.
The resulting fluorenyl containing metallocenes can be used In combination with a suitable co-catalyst for the polymerization of olefinic monomers. In such processes the metallocene or the co-catalyst can be employed on a solid insoluble particulate support.
Examples of suitable co-catalysts include generally any of those organometallic co-catalysts which have in the past been employed in conjunction with transition metal containing olefin polymerization catalysts. Some typical examples include organometallic compounds of metals of Groups IA, IIA, and IIIB of the Periodic Table. Examples of such compounds have included organometallic halide compounds, organometallic hydrides and even metal hydrides. Some specific examples include triethyl aluminum, tri-isobutyl aluminum, diethyl aluminum chloride, diethyl aluminum hydride, and the like.
The currently most preferred co-catalyst is an aluminoxane. Such compounds include those compounds having repeating units of the formula 
where R is an alkyl group generally having 1 to 5 carbon atoms. Aluminoxanes, also sometimes referred to as poly(hydrocarbyl aluminum oxides) are well known in the art and are generally prepared by reacting an organo hydrocarbylaluminum compound with water. Such a preparation techniques are disclosed in U.S. Pat. Nos. 3,242,099 and 4,808,561, the disclosures of which are incorporated herein by reference. The currently preferred co-catalysts are prepared either from trimethylaluminum or triethylaluminum, sometimes referred to as poly(methyl aluminum oxide) and poly(ethyl aluminum oxide), respectively. It is also within the scope of the invention to use an aluminoxane in combination with a trialkylaluminum, such as disclosed in U.S. Pat. No. 4,794,096, the disclosure of which is incorporated herein by reference.
The fluorenyl-containing metallocenes in combination with the aluminoxane co-catalyst can be used to polymerize olefins. Generally such polymerizations would be carried out in a homogeneous system in which the catalyst and co-catalyst were soluble; however, it is within the scope of the present invention to carry out the polymerizations in the presence of supported forms of the catalyst and/or co-catalyst in a slurry or gas phase polymerization. It is within the scope of the invention to use a mixture of two or more fluorenyl-containing metallocenes or a mixture of an inventive fluorenyl-containing metallocene with one or more other cyclopentadienyl-type metallocenes.
The fluorenyl-containing metallocenes when used with aluminoxane are particularly useful for the polymerization of mono-unsaturated aliphatic alpha-olefins having 2 to 10 carbon atoms. Examples of such olefins include ethylene, propylene, butene-1, pentene-1, 3-methylbutene-1, hexene-1, 4-methylpentene-1, 3-ethylbutene-1, heptene-1, octene-1, decene-1, 4,4-dimethyl-1-pentene, 4,4-diethyl-1-hexene, 3,4-dimethyl-1-hexene, and the like and mixtures thereof. The catalysts are particularly useful for preparing copolymers of ethylene or propylene and generally a minor amount, i.e. no more than about 12 mole percent, more typically less than about 10 mole percent, of the higher molecular weight olefin.
The polymerizations can be carried out under a wide range of conditions depending upon the particular metallocene employed, and the results desired. Examples of typical conditions under which the metallocenes can be used in the polymerization of olefins include conditions such as disclosed in U.S. Pat. Nos. 3,242,099; 4,892,851; and 4,530,914; the disclosures of which are incorporated herein by reference. It is considered that generally any of the polymerization procedures used in the prior art with any transition metal based catalyst systems can be employed with the present fluorenyl-containing metallocenes.
Generally the molar ratio of the aluminum in the aluminoxane to the transition metal in the metallocene would be in the range of about 0.1:1 to about 105:1 and more preferably about 5:1 to about 104:1. As a general rule, the polymerizations would be carried out in the presence of liquid diluents which do not have an adverse affect upon the catalyst system. Examples of such liquid diluents include butane, isobutane, pentane, hexane, heptane, octane, cyclohexane, methylcyclohexane, toluene, xylene, and the like. The polymerization temperature can vary over a wide range, temperatures typically would be in the range of about xe2x88x9260xc2x0 C. to about 280xc2x0 C., more preferably in the range of about 20xc2x0 C. to about 160xc2x0 C. Typically the pressure would be in the range of from about 1 to about 500 atmospheres or greater.
The polymers produced with this invention have a wide range of uses that will be apparent to those skilled in the art from the physical properties of the respective polymer. Some of the catalysts are useful for preparing syndiotactic polymers. The term syndiotatic polymer as used herein is intended to include those polymers having segments of more than 10 monomeric repeating units in which the alkyl group of each successive monomeric unit is on the opposite side of the plane of the polymer. Generally, the polymer segments having such syndiotactic microstructure are formed of at least about 40 monomeric repeating units in which the position of the alkyl group relative to the plane of the polymer alternates from one monomeric unit to the next monomeric unit.